you can go into the display properties, then appearance, then advanced. choose the icon selection from the drop menu and you can up the size, but you might wanna go looka round for some new icons cause once you get past a certain size if they icon is not made to be blown up that far they will look kinda ugly and jagged
Yeah, I have to agree with Qumahlin, you have to use "XP" icons with alpha transparency support. I too liked some of the Mac OS icons, so I found some I liked at http://www.deviantart.com and blew them up to size 65 for my desktop. Unfortunately, most programs don't have these type of icons, so you have to change the icon to the XP ones so it looks good.